1. Field of the Invention
This invention relates to a stroller, more particularly to a stroller with an adjustable backrest.
2. Description of the Related Art
FIGS. 1 to 3 illustrate a conventional stroller 1 that includes a leg unit with front and rear legs 111, 112, a seat frame 113 pivoted to the front and rear legs 111, 112, a backrest 12 with left and right supporting rods 121 pivoted to the seat frame 113, and a positioning unit. The positioning unit includes a pair of engaging pins 131 and a pair of positioning seats 13, each of which is pivoted to a respective one of the rear legs 112, and each of which is formed with a plurality of engaging grooves 135. Each of the engaging pins 131 projects from a respective one of the left and right supporting rods 121 to engage releasably a selected one of the engaging grooves 135 in a respective one of the positioning seats 13. Each of the positioning seats 13 is rotatable upwardly and downwardly between an engaging position, in which the respective engaging pin 131 engages the selected one of the engaging grooves 135, and a disengaging position, in which the respective engaging pin 131 disengages from the selected one of the engaging grooves 135. A releasing member 14 includes a pair of pushing members 146, each of which is mounted slidably on a respective one of the left and right supporting rods 121, and each of which-contacts a bottom side of a respective one of the positioning seats 13, a pair of urging members 145, each of which is mounted in a respective one of the left and right supporting rods 121 above a respective one of the pushing members 146 and each of which is connected to the respective one of the pushing members 146, and a handle 141 with a string 143 connected to the pushing members 146 in such a manner that pulling of the handle 141 results in upward movement of the pushing members 146 against urging action of the urging members 145, which, in turn, results in upward movement of the positioning seats 13 to the disengaging position, thereby permitting adjustment of the backrest 12 to a desired position. Each positioning seat 13 is restored to the engaging position by virtue of gravity upon being released from the pulling action of the handle 141.
The conventional stroller 1 is disadvantageous in that, since each positioning seat 13 is simply laid on the respective engaging pin 131 at the engaging position by gravity, the same tends to disengage undesirably from the respective engaging pin 131. Moreover, a longer travelling distance of the handle 141 and a greater pulling force are required to adjust the position of the backrest 12 when the latter is disposed at a lower position.
Therefore, the object of the present invention is to provide a stroller that is capable of overcoming the aforementioned drawbacks of the prior art.
According to the present invention, a stroller comprises: a leg unit; a seat frame mounted on the leg unit; a backrest including a supporting frame that is pivoted to the seat frame so as to permit rotation of the supporting frame about a first axis; and a positioning unit including an elongated positioning seat with a rear end pivoted to the leg unit so as to permit rotation of the positioning seat about a second axis that is parallel to the first axis, and a front end section opposite to the rear end and connected movably to the supporting frame. The positioning unit further includes a first engaging member formed on the positioning seat, a second engaging member mounted movably on the supporting frame and disposed above the first engaging member, and an urging member. The second engaging member is movable upwardly and downwardly on the supporting frame between an engaging position, in which the second engaging member engages the first engaging member, and a disengaging position, in which the second engaging member disengages from the first engaging member. The urging member urges the second engaging member to press downwardly against the first engaging member when the second engaging member is positioned at the engaging position.